The present invention relates to a filter element for fluids which provides a large filter surface area in a compact volume.
Published German patent application no. DE 196 08 589 discloses a filter element for gaseous or liquid media which can be inserted into a filter housing. The filter element has a filter medium that is pleated in a zigzag pattern and closed to form a ring. End disks are arranged on the ends of the filter medium. Fluid flows through the filter element from the inside to the outside, so the particles of dirt striking the filter element form a filter cake on the surface of the filter element. This is understood to improve the filter fineness of the filter medium. In certain use situations, such filters may also be used without a housing, so an outer supporting jacket is needed for such an application. In the state of the art, this is accomplished by a perforated outer jacket. The outer jacket is made either of perforated sheet metal or a corresponding perforated plastic part.
To achieve especially large filter surface areas, it is necessary to utilize double rings of filter material having an annular space, arranged between the inner and outer rings of filter material. The annular space receives the oncoming flow of dirty fluid to be filtered, which makes it necessary to achieve an eccentric oncoming flow. This is accomplished by having an eccentrically positioned flow inlet opening. However, an eccentrically positioned inlet opening poses problems when connecting the filter element. To make it possible to effect a central connection, it is known in the art to use adapter plates which produce a re-direction or diversion of the flow. However, the increased structural height of such adapter plates is disadvantageous because it reduces the filter area and/or increases the installation space required for the filter element.